The invention relates to a gasket, in particular, a gasket for a motor vehicle component which has at least one sheet-metal layer which has at least one screw hole for the passage of the threaded shaft of a screw.
Vehicle manufacturers require from their suppliers to an ever increasing extent that the latter supply structural parts together with associated components in a preassembled state; however, even when a supplier supplies a structural part without associated components, the latter are often already fitted to the structural part in the works of the vehicle manufacturer before this part is brought to the assembly line for assembly.
Assembly screws are customarily part of a gasket, in particular, flat gaskets, and during the course of the endeavors described above it is required that the gasket be supplied to the assembly line together with assembly screws, wherein the screws are intended to be held on the gasket in a manner secured against loss.
Means for securing screws against loss are known in various designs; for example, DE-U-87 08 965 discloses a cap screw with a washer which is produced from an elastic plastics material and has a screw hole for the passage of the threaded shaft of the cap screw as well as a means for securing the cap screw against loss in order to hold the latter on the washer. Four holding tongues, which are all located in a plane common to the holding tongues prior to the insertion of the cap screw into the screw hole of the washer, are integrally formed at the edge of the screw hole of the plastic washer, and the cap screw has between its head and its threaded shaft an annular groove, into which the holding tongues engage once the threaded shaft has been pushed through the screw hole of the washer under elastic deflection of the holding tongues.
Modern gaskets for motor vehicles often have a metallic gasket plate consisting of one or several sheet-metal layers which are coated, where applicable, over the entire surface or partially with a mostly elastomeric coating material, and the object underlying the invention was to provide a means for securing screws against loss for a gasket with at least one sheet-metal layer, wherein the means for securing against loss is intended to be simple to produce and not lead to complications during the assembly.
Proceeding from a gasket having at least one sheet-metal layer which has at least one screw hole for the passage of the threaded shaft of a screw, this object may be accomplished in accordance with the invention in that several holding tongues which are integral with the sheet-metal layer and are distributed over the hole circumference and arranged at a distance from one another project from the edge of the screw hole, that the edge regions of the holding tongues facing the center of the holexe2x80x94when seen in axial direction of the screw holexe2x80x94define a circular core hole, the diameter of which corresponds to the core diameter of the screw thread, that the width of the holding tongues as well as the thickness of the sheet-metal layer make the engagement of the holding tongues in the screw thread possible at least in the edge regions of the holding tongues facing the center of the hole, and that at least some of the holding tongues are bent out of the plane of the sheet-metal layer in such a manner that the edge regions of the holding tongues facing the center of the hole are arranged so as to be offset in relation to one another in axial direction of the screw hole in accordance with the pitch of the screw thread.
Holding tongues designed in this manner may be punched out as well as bent with a punching-bending tool during the production of the screw hole, where applicable even during the course of punching out the sheet-metal layer with simultaneous production of the screw hole, wherein the tool can, of course, be designed such that the sheet-metal layer falls of its own accord out of the tool following the punching-bending procedure. If the sheet-metal layer originally has a sheet-metal thickness which would not allow the holding tongues to engage in the screw thread, the sheet-metal thickness of the edge regions of the holding tongues facing the center of the hole can also be easily reduced with the tool by way of stamping such that these edge regions can then engage in the screw thread. In contrast to a means for securing against loss, with which all the holding tongues or rather their edge regions facing the center of the hole are all located in one and the same plane so that only one of the holding tongues can engage in the screw thread when the screw is inserted into the screw hole without any deformation of the holding tongues, the inventive means for securing against loss makes it possible for all the holding tongues to engage in the screw thread, the screw to be held on the gasket in a manner really secure against loss, namely with the screw axis running at right angles to the plane of the sheet-metal layer, and for the screw to be centered in the screw holexe2x80x94this represents a quite considerable advantage for the later assembly. Moreover, the inventive means for securing against loss also leads to the following, additional advantages: If the screw is turned during its insertion into the gasket, no expenditure of force whatsoever is required; the elastically deflectable holding tongues also, however, allow the screw to be easily inserted into the screw hole without turning it whereas any screwing back of the screw is not possible or only with a relatively high expenditure of force.
In principle, it would be possible to bend the holding tongue or the holding tongues to be bent out of the plane of the sheet-metal layer such that it extends or they extend at an angle to the plane of the sheet-metal layer. However, embodiments are preferred, with which each holding tongue bent out of the plane of the sheet-metal layer is bent at an angle not only in the area of its base but also close to its edge region facing the center of the hole in such a manner that the edge region extends at least approximately parallel to the plane of the sheet-metal layer since, in this case, the edge regions of all the holding tongues close to the center are located at right angles in the screw thread.
The inventive means for securing against loss is of a particularly simple design when one of the holding tongues is flat and located in the plane of the sheet-metal layer since, in this case, only the second or all the other holding tongues has or have to be bent out of the sheet-metal layer.
A particularly effective means for securing against loss and a particularly good centering of the screw result when the edge regions of the holding tongues facing the center of the hole have a contour in the shape of a circular arc corresponding to the core hole although embodiments are, of course, also conceivable, with which the edge regions of the holding tongues facing the center of the hole have, for example, a triangular or convexly semicircular contour.
So that the holding tongues can engage well in the screw thread without them having to be deformed during the insertion of the screw into the screw hole, the edge regions of the holding tongues facing the center of the hole ought to be relatively narrow, for which reason embodiments with more than two holding tongues are preferred with respect to the desired centering of the screw in the screw hole, particularly embodiments with three holding tongues arranged at equal angular distances from one another.
Finally, it is recommended to design the inventive means for securing against loss such that the holding tongue or holding tongues bent out of the plane of the sheet-metal layer projects or project from the sheet-metal layer in assembly direction of the screw since, in this case, no overly considerable expenditure of force is required in order to be able to insert the screw into the screw hole without turning it, namely in the direction, in which the holding tongues have been bent out of the sheet-metal layer.